Plaster of Paris casts have been used to immobilize body members for some time. These bandages are made by depositing plaster of Paris on reinforcing scrim material such as gauze. The plaster of Paris is activated by dipping the cast bandage in water and then applying the bandage to a patient. In recent years, new casting materials have replaced plaster of Paris as the hardening agent in the cast bandage. This new material is a water hardenable polyurethane. After curing the polyurethane offers advantages over plaster of Paris in that it allows transmission of x-rays through the finished casts and it is not sensitive to water as is plaster of Paris and it is also considerably lighter for a given strength in plaster of Paris.
With the use of plaster of Paris bandages, it is common to provide for reinforcement of selected areas of the cast by applying additional bandage material to a particular section of the cast which was desired to be reinforced. For example, if the cast was a walking cast, it was quite common to put a reinforcing layer of plaster of Paris around the sole of the foot of the cast and to incorporate a plug of some type so that the patient could place the cast onto the ground when walking with crutches without fear of the cast breaking. With the advent of the polyurethane casting materials, reinforcement has been performed in substantially the same manner; that is additional strips of the polyurethane impregnated substrates have been applied to the cast where reinforcement is desired. The application of additional strips or segments of polyurethane casting tape is somewhat difficult because of the nature of the polyurethane polymer which is the hardening material in these tapes. The polyurethane becomes tacky during the curing cycle before it begins to harden. It is difficult for one person to cut a piece of polyurethane casting tape, wet the cut tape and then apply the cut section to the cast to obtain the reinforcement and smooth the reinforcement section into the cast while the tape is tacky. The polyurethane casting tapes harden rapidly and lose their tackiness and it is difficult to finish the reinforcement before the tape cures and hardens.